Method for saccharifying cellulosic materials by means of diluted mineral acids



Aug. 22, 1944. F. c. BOINOT 2,356,500

METHOD FOR SACCHARIFYING CELLULOSIC MATERIALS BY MEANS OF DILUTED MINERAL ACIDS Filed April 18, 1942' .9 .dtl orrzqy.

Patented Aug. 22, 1944 METHOD FOR sAccnARrFrmG CELLULOSIO MATERIALS BY MEANS OFDILUTED MIN- ERAL ACIDS .Firmin Charles Boinot, Mae-mute the Alien Property Custodian vested in V Application April 18,1942, Serial No. 439,604

' "In France March 27,1941

. 4 Claims. (01. 121-131) Processes' for saccharifying cellulose by reacting diluted mineral acids at a raised temperaturewith suitably divided starting material'are already known. The necessity of withdrawing as soon as possible thesugarthus produced to subsequent detrimental action of acid and'heat has been recognized by some authors.

As a matter of fact, it has been proposed a a process wherein restricted amounts of diluted acid solutions(0.1 to 0.4 per cent) are intermittently passed through cellulosic material in abattery ofpercolators under pressure and at increasing temperature, in order periodically to expel from the reaction zone the sugar produced therein, the proportion being of 5 to parts of acid solutionfor 1 part of cellulosic material to be treated.

While the foregoing process brings about substantial improvement over prior processes as' concerns sugar destruction, it is far from solving the problem in a thoroughly satisfactory manner.

As a matter of fact, it is well known thatone washing of the material in one vessel cannot provide for thprough removal of the sugar contained therein. Hence, the sugar removal by intermittently adding diluted acid, -while fresh sugar is produced in the meantime, can be only partial and a considerable proportion'of sugar remains in the reaction vessel wherein it is obviously decomposed during subsequent heating in the presence of further amounts of acid.

battery, the liquid used as a vehicle being preferably that diluted. acid solution which will be employed for the next hydrolysis. The whole amount of sugar produced in eachstep is thus removed and a starting material thoroughly freed from sugar is forwarded to step. Another feature of this invention is as follows: the-successive hydrolysis treatments to which starting material is subjected are performed at increasing temperatures and with decreasing acidities. a

the next cooking A still further feature of this invention comprises subjecting to hydrolysis a cellulosic material containing only that amount of acid which has been absorbed by its pores, l. e. without any covering or coating liquid. It is thus possible to obtain less diluted sugar solutions than according to other known processes.

" larger number of hydrolyses' material but it is obviously within the ambit of this invention to subjectcellulosic material to a The concentration of acid liquor and the cooking temperature in each one of the successive treatments may vary .within fairly broad limits according to thenature of wood under consideration. By way "of merely indicative example,

' acidities of 6 to 2 grams oi-'10 to 3 grams per litre may be employed according as hydrochloric acid or sulphuric acid is resorted to; as to temper ature, it may vary from 150 to 200 C.

It has been found advantageous to deacidify the material remaining after the last hydrolysis and consistingof' entirely exhausted lignin by methodically washingit with'hot or cold water. Deaciclification is favourable in the respect of further use of lignin, particularly for the manufacture therefrom of a high grade charcoal adapted to be employed in automobile vehicle gas producers." 7

According tothe species of wood. the'alcohol yield varies from-220 to 280 litres perl,000 kg.

Broadly speaking, four successive hydrolyses with intervening methodical diffusion as above set forth will be sufficient for exhausting the starting of dry wood. The acid consumption'ranges'from about "8.51 kg; to about 16.5 kg. per 100 litres of. alcohol according as the case maybe.

In spite of the use'of diffusion batteries between successive hydrolyses; the apparatus is relatively simple and inexpensive as a large num-- ber of its component parts particularly the diffusion elements can be made of .wood.

The following example which is not limitative will showwith'reference to the accompanying drawing, the manner in which this invention may be carried out into practice. I

The apparatus shown on the drawing comprises four units l, 2, 3, 4 each of which includes an acidulatedwater tank A, a cooking-vessel C and a diffusion battery D. The first unit further comprises a humidifying tank B in whichv acid solution impregnates the starting material.

Wood comminuted into chips is fed through pipe I to tank B wherein it is acted upon by acid solution at a temperature of C. from tank A1, the solution being an aqueous solution containing 5 grams of hydrochloric acid per litre. After being contactedfor 30 minutes the wood mass has absorbed 2.5 times its weight of acid solution. Afterdrainage, it is dumped into the cooking vessel C1 having a capacity of hectolitres wherein it is cooked during;45 minutes pacity of 100 hectolitres, wherein it is countercurrently, contacted in usual manner with an aqueous solution containing 4 grams of acid per litre which is supplied from tank A2 at a tem perature of 90 0. through pipe 2.

I about 175 c.

A solution havinga large content; or pentoses and further including a little hexoses flows through pipe 3 and is gathered in collector 8.

Excess washing liquid flowing out of each diiiul sion element is recovered inpipe 4 and returned to tanlrAa.

As to starting material thoroughly freed from sugar and impregnated with acid liquor having an acid content of 4 grams per .litreyit is elevated after draining by raising means 5 of an kind to the cooking vessel C: of the second unit wherein remainder of sugar solutions, as it has a high .pentose content and the pentoses may be conwater, theimoist mass thus obtained being then it is subjected for minutesto a cooking-treat I ment under .steam pressure of 8 kg. per square centimeter corresponding to a temperature of From cooking Cz', the'material is dumped into diiiusion battery D: wherein it is .washed .with water having acid content of 3 grains/per litre coming from tank'Aa A solution containing an amount of sugar corresponding to thorough exhaustion of the starting material is withdrawn from thedischar'ge part-ofthe battery. I

' A like process takes place in. cookingvessel C: and in battery D thel-acidsolution used in the latter having .an acid content of 2.5 grams per litre and the pressure incooking vessel Ca being 12 kg. per square centimeter corresponding to a temperature of 185 C. Cooking istperformed during 15. minutes. Again the withdrawal of sugar liquid from D; is so controlled as to secure thorough exhaustion of the material.

In the last cooking vessel C4 the steam pressure is about atmospherescorresponding to a temperatureof 195 C. and the. duration of the cooking process can be as short as 7 minutes. The washing liquid used indiifusion-battery D4 is water preferably. heatedto 90. C. From the discharge end of battery D4, there is obtained on the one hand a sugar solution which is removed in the same way as; the preceding ones, for instance through-collector S,'on the other hand pure water which is discarded through pipe and finally exhausted deacidiiled-lignin which may be employed for any purpose, P ticularly for manufacture of charcoal for gas producers (conduit 1)."

The above describedplantcan be modified in various respects withoutdeparting from thespirit of this invention. Particularly it may be advantageous to provide cooking vessels of decreasing I sizes from the first one to the last one in order to make allowance for the volume reduction suffered by the startingmaterial as the treatment proceeds. The" following sizes may be adopted as an example: 1

First unit: p

01,100 hectolitres Y D1, 6 diffusors of 100 hectolitres Second unit:

C2, 80 hectolitres i D2, 6 difiusors of 80 hectolitres Third unit: i C3, 62 hectolitres D3, 6 dii'fusors of 62'hectolitres Fourth unit:

C4, 50 hectolitres. D4, 6 difl'usors of 50 hectolitres. Again the sugar solutions obtained from each 'diflusionstep can be mixed together or separately recovered. p a A j Still again only the liquid irom the first diffu sion step maybe gathered separately'irom'the admixed for the next hydrolysis with such a mass of acid that suitable acidity will be secured without the lvolumetof liquid retained by the material being increased. l

. The method according to this invention is valuablefor treating not only wood chips or saw-dust but also all cellulosic materials of any type whatever.

The. sugar solutions manufactured in accordance with this invention may be treated for recovering the sugarscontained therein or subiected toany fermentation for converting them 1mm valuable products for instance alcohol. In

the latter case it is advisable to employ the yeast reuse method described and claimed in U. S. Patent 2,054,736.

What I claim is: V I

,1. A method for gradually saccharifying cellulosic material which comprises passing said material successively through a plurality of separate cooking zones and desugaring' zones in alternatiing sequence, each successive coating zone being maintained at a higher temperature, the material being cooked in each cooking zone for a predetermined time with an aqueous weak mineral acid solution to produce sugar therefrom, and subjected to exhaustive diffusion with an aqueous liquid having a less acid content than said cookingsolution, for removing the whole amount of sugar from said material and saturating the same with acid for the next cooking step so that the next cooking step is performed with a weaker vacid solution than the previous step.

2. The method of claim 1, further comprising the step of draining the cellulosic material after :gch desugaringstep for lowering its liquid con- 3. ,The method of claim 1, which further comprises collecting separately the sugar solution from the first desu'garing zone and the sugar solutions from the other desugaring zones.

- 4. A method for the manufacture of sugar from cellulosicmaterial, which comprises passing said material successively through a plurality of separate cooking zones and desugaring zones in alternating sequence; cooking the material in the firstcooking zone at a temperature of at least 150 C. with an aqueous, acid solution containv ing no more than 10 grams of a mineral acid per litre to obtain a sugar containing product; subjecting the product in the next following desugaring zone, to exhaustive difiusion with a hot aqueous acid solution having a lower content of the same mineral acid than the first solution, thereby obtaining a sugar containing solution and a de..

sugared cellulosic material charged with the secend-named acid solution; draining the desugared cellulosic material before passing it to the next following desugaring zone; effecting the following cooking treatments at higher and higher temperatures,'the last one at a temperature not above 200 C.; and effecting the following difiusions with hot aqueous solutions having lower and lower contents of. said mineral acid, the last diffusion being performed with pure water. I

1 FIRMIN CHARLES BOINOT. 

